A device for simultaneously detecting different gas components is disclosed in U.S. Pat. No. 5,298,146. This device includes a multiplicity of working electrodes, a common counter electrode and a common reference electrode within an aqueous electrolyte. The working electrodes are mounted segment-like behind a planar diffusion membrane and are subjected to the gas components to be detected via individual orifices which limit the entry of the gas. The orifices are mounted forward of the diffusion membrane. The formation of the measurement value takes place with the aid of a potentiostatic evaluation circuit which selects and controls the potentials at the working electrodes.
It is a disadvantage of this known device that all gas components diffuse through the diffusion membrane and, in this way, can reach all measuring electrodes. This leads especially to incorrect measurements when the entry to the measuring electrode for a gas component must be delimited by a diffusion barrier and/or by a selective filter. The diffusion barrier can, for example, be used when measuring oxygen. A further disadvantage is that the projection surface at the gas side can be utilized only incompletely because insulating intermediate spaces must remain between the electrodes. This is especially the case when trace gases are to be detected. A further disadvantage is that the fixing and insulation of contact leads is complex for a coplanar measuring electrode arrangement.